The Nature vs. Nurture Debate

1. The Nature vs. Nurture Debate

before you start

Think about this: are we who we are because of nature (biology and genetics), or are we who we are because of nurture (our environment, culture, and learned behaviors)?

That question is a longstanding enigma known in psychology as the nature vs. nurture debate. For decades, scholars have carried on the nature vs. nurture debate, which seeks to understand the extent to which our personalities and traits are the product of our genetic makeup and biological factors, and the extent to which they are shaped by our environment, including through our experiences with our parents, peers, and culture.

think about it

• Why do biological children sometimes act like their parents—is it because of genetics, or because of the early childhood environment and what the child learned from their parents?
• What about children who are adopted—are they more like their biological families or more like their adoptive families?
• How can siblings from the same family be so different?

For any particular feature, those on the nature side of the debate would argue that heredity plays the most important role in bringing about a feature in an individual. Nativism is the extreme nature position in the debate. Nativism is the belief that human characteristics (e.g., personality, mental abilities, as well as hair color, eye color, skin pigmentation) are a result of evolution and variation between and across individuals is due to genetics.

The emphasis is on heritable traits, or traits that can be passed down from parents to offspring. The connection of a trait to nature is strengthened by when the trait appears—the earlier it appears, the more it is attributed to genetics.

Those on the nurture side of the nature vs. nurture debate, however, would argue that one’s environment is most significant in shaping the way we are. Empiricism is the extreme nurture position. Empiricism is the belief that the human mind is a blank slate at birth (also known as tabula rasa), and an individual’s experiences fill-in this blank slate. If we take on this position of the nature-nurture debate, then any psychological and behavioral characteristics are a result of learning. The only biological aspect is related to maturation; otherwise, how you are raised governs infant and child development. This debate continues in questions about what makes us masculine or feminine (Lippa, 2002), concerns about vision (Mutti, Zadnik, & Adams, 1996), and many other developmental issues.

big idea

Some people argue that our traits and abilities are set before birth, because who we are is based entirely on nature—our genetics or biological makeup. Other people assert that who we are is a result of nurture—our social relationships with others, the cultures and environments we live in throughout our lives, and our lifestyle choices.

terms to know

Nature vs. Nurture Debate

The classic debate over whether human behavior is best explained by biological programming or social and cultural influence.

Nature

The influences of biology and genetics on behavior.

Nativism

The belief that human traits and characteristics are a result of evolution, and variation between and across individuals is due to genetics.

Heritable Traits

Traits that can be inherited or passed down from parents to offspring.

Nurture

Environmental, social, and cultural influences on behavior.

Empiricism

The belief that human traits and characteristics are the result of environmental influences.

2. The Epigenetics Framework

Now that you are familiar with the nature versus nurture debate, you might be wondering “is there a position that incorporates both?” There can certainly be an interaction between nature and nurture, and this perspective is called epigenetics. Epigenetics is the study of how environmental experiences affect genetic activity, without changing the genetic makeup of an individual. They are reversible changes, and modify how our body reads our genetic material (like when a gene is turned on or off).

hint

The prefix of epigenetics is epi-, which means above, meaning that the term epigenetic means above the genome.

In epigenetics, we recognize that while we are all born with specific genetic traits inherited from our parents, such as eye color, height, and certain personality traits, there is also a deep interaction between our genes and our environment. Our unique experiences in our environment influence whether and how particular traits are expressed, and at the same time, our genes influence how we interact with our environment (Diamond, 2009; Lobo, 2008). There is a reciprocal interaction between nature and nurture, as they both shape who we become, though the debate continues as to the relative contributions of each.

Most scholars agree that there is a constant interplay between the two forces. It is difficult to isolate the root of any single behavior as a result solely of nature or nurture, and most scholars believe that even determining the extent to which nature or nurture impacts a human feature is difficult to answer. In fact, almost all human features are polygenic (a result of many genes) and multifactorial (a result of many factors, both genetic and environmental). It is as if one’s genetic make-up sets up a range of possibilities, which may or may not be realized depending upon one’s environmental experiences.

EXAMPLE

A person might be genetically predisposed to develop diabetes or other chronic conditions, or the person’s lifestyle (e.g., poor diet, lack of exercise) may help bring about the disease.

Developmental psychologist Gilbert Gottlieb has suggested that genetics and environment interact to affect gene expression and developmental outcomes. An example of this is sickle cell anemia, a genetic disorder that causes abnormal blood oxygen levels due to red blood cell characteristics. An individual with sickle cell anemia can experience a sickle cell crisis when oxygen deprivation occurs, which can cause health complications. The environment of an individual with sickle cell anemia will affect that individual’s phenotype, affecting gene expression and developmental outcomes (Gottlieb 1998, 2000, 2002).

The following illustration shows how genetics and environmental influences combine to create a unique phenotype for each individual. Phenotype refers to an individual’s inherited physical characteristics and observable traits, such as height, eye color and blood type. A person’s phenotype is determined by both their genetic makeup (genotype) and environmental factors. A person’s phenotype and genotype are determined by their chromosomes.

key concept

Chromosomes are long threadlike structures found in a cell nucleus that contain genetic material known as deoxyribonucleic acid (DNA). In each chromosome, sequences of DNA make up genes that control or partially control a number of visible characteristics, known as traits, such as eye color, hair color, and so on.

terms to know

Epigenetics

The study of how environmental experiences affect genetic activity without changing the genetic makeup of an individual.

Polygenic

A feature that is a result of many genes.

Multifactorial

A result of many factors, both genetic and environmental.

Phenotype

An individual’s inherited physical characteristics and observable traits, such as height, eye color, and blood type.

Genotype

The genetic makeup of an individual.

Chromosomes

Long threadlike structures found in a cell nucleus that contain genetic material known as deoxyribonucleic acid (DNA).

Deoxyribonucleic Acid (DNA)

The molecule that carries genetic information for the development and functioning of an organism.

3. Types of Epigenetic Changes

There are various types of epigenetic changes that can occur. Consider these three:

• Deoxyribonucleic Acid (DNA) Methylation. This is a process that adds molecules called methyl groups to a specific place on the DNA, which shuts the gene “off” because the protein that normally attaches to a particular location within the DNA to turn the gene “on” is blocked by the newly added methyl group. In order to turn the gene back “on,” demethylation would have to occur.
• Histone Modifications. Histone is a protein that provides structural support for a chromosome. Each chromosome contains a long molecule of DNA, which must fit into the cell nucleus. To do that, the DNA wraps around complexes of histone proteins, giving the chromosome a more compact shape. Histones play a role in the regulation of gene expression. Typically, DNA wraps around histone proteins. The gene is turned “off” when DNA is inaccessible due to tightly packed histones, which lends no access to proteins that “read” the gene. Contrarily, if histones are loosely together or DNA is exposed in some way, proteins that “read” and thereby turn “on” the gene can do so. Certain chemicals impact the extent to which histones are packed together, which then dictates whether DNA is accessible or not and if the gene is “on” or “off.”
• Non-Coding RNA. This is DNA that also functions to instruct the coding and non-coding of ribonucleic acid (RNA), which is a single-stranded molecule (as opposed to the double-stranded DNA) that converts the genetic information contained within DNA to a format used to build proteins. Non-coding RNA can break down coding RNA so that protein production does not occur, which further helps control whether a gene is “on” or “off.” In the instance of histone modification, non-coding RNA can assist with modifying histones to alter gene expression (Centers for Disease Controls and Prevention, 2022).

try it

Let’s apply the epigenetics framework to your life. First, select any two traits that you are interested in knowing more about. It could be anything from your IQ, to height, weight, hair color, or personality. On a piece of paper, write one of the traits at the top and create two columns—one for nature and the other for nurture. Write down things that you know about your trait that may be attributed to genetics or the environment. For instance, if you select IQ, then consider the IQ of your immediate family and relatives. Do you see a pattern emerging at all? Consider environmental factors such as education, family income, physical activity, and parental occupation and their association with IQ. After you complete this activity with one trait, do it for your other trait. In looking at the traits you selected, was one more easier to analyze from the nature/nurture lens?

terms to know

Deoxyribonucleic Acid (DNA) Methylation

A process that adds molecules called methyl groups to a specific place on the DNA, shutting the gene off.

Histone Modifications

Changes to histone proteins that provide structural support for chromosomes, influencing the regulation of gene expression.

Non-Coding RNA

A form of RNA that can break down coding RNA so that protein production does not occur, which further helps control whether a gene is “on” or “off.”

Ribonucleic Acid (RNA)

A single-stranded molecule that converts the genetic information contained within DNA to a format used to build proteins.

REFERENCES

Centers for Disease Control and Prevention. (2022, August 15). What is epigenetics? Centers for Disease Control and Prevention. Retrieved December 30, 2022, from www.cdc.gov/genomics/disease/epigenetics.htm

Centers for Disease Control and Prevention. (2022, August 18). What is sickle cell disease? Centers for Disease Control and Prevention. Retrieved December 30, 2022, from www.cdc.gov/ncbddd/sicklecell/facts.htm

l Diamond A. The interplay of biology and the environment broadly defined. Dev Psychol. 2009 Jan; 45(1):1-8.

Gottlieb, G. (1998). Normally occurring environmental and behavioral influences on gene activity: From central dogma to probabilistic epigenesis. Psychological Review, 105, 792-802.

Gottlieb, G. (2000). Environmental and behavioral influences on gene activity. Current Directions in Psychological Science, 9, 93-97.

Gottlieb, G. (2002). Individual development and evolution: The genesis of novel behavior. New York: Oxford University Press.

Lippa, R. A. (2002). Gender-related traits of heterosexual and homosexual men and women. Archives of sexual behavior, 31(1), 83-98.

Lobo, I. (2008) Environmental influences on gene expression. Nature Education 1(1):39

Mutti, D. O., Zadnik, K., & Adams, A. J. (1996). Myopia. The nature versus nurture debate goes on. Investigative Ophthalmology & Visual Science. Retrieved May 03, 2011, from www.iovs.org/cgi/reprint/37/6/952

National Human Genome Research Institute. (n.d.). Talking Glossary of Genomic and Genetic Terms. Genome.gov. Retrieved January 4, 2023, from www.genome.gov/genetics-glossary/

Newton, R. (n.d.). Genetics and Heredity. Human Growth and Development. Retrieved January 7, 2023, from pressbooks.pub/mccdevpsych/chapter/2-2-genetics-and-heredity/